Abstract: A rack-to-rack packaged semiconductor device exchanger has a length with a midpoint thereof, and includes an inner portion, a first outer rail and a second outer rail on opposite edges of the inner portion for accepting from opposite ends of the exchanger a first rack and a second rack configured to store packaged semiconductor devices therein. At least a first stopper has a retractable extended position which protrudes from the first outer rail for stopping the first rack or second rack from advancing past a location near the midpoint of the exchanger only from one direction. The first stopper and a second stopper can both be included.